Demo: PPL/A

Switching on carburettor heating lets warmer, less dense air into the engine, reducing power and causing RPM to decrease. The other answers are incorrect because angle of attack is not affected and RPM does not increase.

During take-off, carburettor heating must be off because it reduces engine power. In other phases, the power loss is less critical, so heating can be used if needed.

Cooling fins increase the cylinder's surface area, allowing heat to be transferred quickly to the surrounding air. The other options are incorrect because they misinterpret airflow or do not accurately describe the fins' function.

If the oil filter clogs, a bypass valve opens so oil keeps circulating, but debris is no longer filtered out. The other answers are wrong: there is no alternate filter, and oil circulation does not stop after 15 or 30 minutes.

An Otto engine should be shut down by completely leaning the mixture, which stops fuel flow and combustion. Shutting down the generator, closing the throttle, or feathering the propeller does not reliably stop the engine.

Mixtures with a high amount of fuel are called 'rich' because they contain more fuel than air. 'Lean' means less fuel, 'full' and 'empty' do not describe mixture ratios.

As altitude increases, air pressure drops and less oxygen enters the engine. With unchanged mixture, the fuel amount stays the same, so the mixture becomes richer. The other answers are wrong: the mixture does not become leaner, stay constant, or become liquid.

The correct answer lists all systems where temperature is actually measured: engine lubricant, cooling fluid, cylinder head, exhaust gas, outside air, and cabin air. The other options include incorrect or incomplete items, e.g., altimeter or directional gyro do not measure temperature.

The correct answer is right because each tank must have its own indicator, calibrated to read 'zero' in level flight when only unusable fuel remains. The other options either require too few indicators, incorrect calibration, or extra, unnecessary systems.

The Pitot/static system measures total and static air pressure, which is essential for determining airspeed and altitude. It does not prevent Pitot tube icing, correct the airspeed indicator to zero on the ground, or prevent static buildup.

The Pitot tube measures total air pressure, which is the sum of static and dynamic pressure. It does not measure only static or dynamic pressure, and it is unrelated to cabin air pressure.

QFE is the barometric pressure at a reference datum, typically the runway threshold. The other options refer to sea level pressure, altitude above 1013.25 hPa, or magnetic bearing, which do not define QFE.

The correct answer is: altitude above the reference pressure level 1013.25 hPa. QNE is the altitude indicated when the altimeter is set to 1013.25 hPa. The other options refer to different types of pressure, not QNE.

The altimeter subscale is used to reference the altimeter reading to a specific pressure level, such as mean sea level, aerodrome level, or standard pressure (1013.25 hPa). The other options are incorrect because the subscale does not adjust for temperature or system errors.

If the subscale is set to a higher than actual pressure, the altimeter shows too high. The aircraft is closer to the ground than indicated. The other answers confuse the effect or describe the opposite situation.

A lower-than-standard temperature causes the altimeter to indicate too high. This is because denser air makes the altimeter overread. The other options are incorrect: they either state the opposite, suggest perfect correction, or confuse with Pitot tube issues, which do not affect the altimeter.

True altitude is an altitude above mean sea level corrected for non-standard temperature and QNH. This gives the actual height above sea level. The other options refer only to ground level, pressure, or temperature, which is incorrect.

The altimeter uses an aneroid capsule that reacts with delay to pressure changes due to hysteresis. The vertical speed indicator and tachometer are less affected. The direct reading compass is not pressure-based and thus not affected.

Altitude measurement is based on static pressure, which decreases as altitude increases. Total, dynamic, and differential pressures are used for other instruments like the airspeed indicator, not the altimeter.

Correct: The vertical speed indicator measures the rate of change of static pressure by comparing current static pressure with that inside a reservoir. The other options are incorrect: they mention total pressure, vacuum, or acceleration, which are not how the instrument works.

The vertical speed indicator measures the difference between the present static pressure and the static pressure of a previous moment. This shows climb or descent rate. The other options are incorrect because they refer to dynamic or total pressure, which are not used by the VSI.

Calibrated airspeed (CAS) is indicated airspeed (IAS) corrected for instrument and position error. The other options are incorrect because they refer to different speeds or corrections not related to the definition of CAS.

TAS increases with altitude due to thinner air. You can estimate it by adding 2% of the CAS for every 1,000 ft. The other options are incorrect because they either subtract, use too high a percentage, or use the wrong unit (meters instead of feet).

The airspeed indicator shows indicated airspeed (IAS), which is lower than true airspeed (TAS) at 5000 ft. With 110 kt TAS at 5000 ft, IAS is about 100 kt. The other answers are too high or too low for this altitude and speed.

The airspeed indicator works by measuring total air pressure and comparing it to static air pressure. The other options are incorrect because they mention vacuum comparison, direct display, or only dynamic pressure, which do not describe the actual principle.